This application claims the benefit of International Application No. PCT/EP99/09144, filed Nov. 22, 1999, and European Patent Application No. 99200246.9, filed Jan. 29, 1999.
This invention relates to an aluminium product to be joined by brazing or soldering to another aluminium product.
Such a product is generally known in WO-A-98/51983 and all technical information disclosed is that patent application is incorporated by reference in this description.
It is common practice to join aluminium components by disposing an aluminium brazing alloy between or adjacent to the component surfaces to be joined, and heating the brazing alloy and the joining surfaces in appropriately assembled fashion to a temperature (brazing temperature) at which the brazing alloy melts while the components remain unmelted. Upon subsequent cooling the brazing alloy forms a filet or joint that bonds the joining surfaces of the components. For assured selective melting of only the brazing alloy in the heating step, it is commonly preferred that the melting point of the brazing alloy be at least 30xc2x0 to 40xc2x0 C. lower than that of the metal of the components. An example of a typical aluminium brazing alloy is an aluminium-silicon eutectic composition, which starts to melt at about 577xc2x0 C.
The use of clad composite aluminium brazing sheet to join aluminium alloy components is well known. Brazing sheet is used to manufacture heat exchanger components such as tubes, fins, headers, tanks, flow dividers, etc. However an important limitation is that it is difficult to manufacture complicated profiles only using rolled sheet. For complicated profiles such as e.g manifolds or micro tubes, the extrusion process may offer a more cost efficient and better quality solution. One disadvantage of using extruded profiles is has been a problem furnishing extrusions with a braze alloy coating.
The CD process is one of the methods that have been developed in order to produce a braze xe2x80x9ccladxe2x80x9d extruded profile. In this process the profile is coated with AlSi particles coated with NOCOLOK flux Adhesion of the coating is achieved through the use of a binder (polymer). The addition of AlSi particles provides filler metal for braze joints during the brazing process.
In the xe2x80x9cBrazelinerxe2x80x9d process the profile is coated with a mixture of NOCOLOK and particulate AlSi-alloy. Adhesion of the coating is achieved through the use of a binder@x (polymer). The AlSi particles melt and flow during brazing.
The Sil flux process is a method where the profile is coated with a mixture of NOCOLOK and fine Silicon particles. Adhesion of the coating is achieved through the use of a binder. (polymer). During brazing the Si diffuses into the surface and forms a eutectic AlSi alloy thus creating filler metal for braze joints xe2x80x9cin situxe2x80x9d.
A disadvantage with all the above processes is the use of a binder. The binder tends to xe2x80x9cpoisonxe2x80x9d the furnace atmosphere and also presents an environmental issue. In order to overcome these problems costly furnace modifications have been required. For the Sil-Flux process also Silicon erosion tends to be more pronounced due to the presence of particulate Silicon.
Arc flame spray coating is another method where the profile is coated with an AlSi alloy. During this process a lot of oxides is introduced that is undesirable in the brazing/soldering operation.
With all the above efforts to produce an extruded product with a pre-placed filler metal, it still remains a problem in the industry.
It is therefor an object of the invention to provide an aluminium product in which the above mentioned problems are avoided.
This object is achieved in that the position of the outer surface of the first aluminium product which will be connected to the second aluminium product is provided with at least one recess in which there is locked an amount of brazing material.
By means of this xe2x80x9cmechanicalxe2x80x9d assembly it is possible to provide an aluminium product in an integrated manner with the amount of brazing material without the need to use special compositions in order to adhere the brazing material to the aluminium product. It becomes even possible to use commercially available brazing materials, which after being locked in the recess allow the aluminium product to be handled in a normal way, such that the brazing material stays in place during subsequent handling or fabrication operations such are shipping, machining, forming, stamping, cutting, washing or degreasing.
In a preferred embodiment of the invention each recess has the shape of a groove and the amount of brazing material has the shape of a wire.
In this way it becomes possible to use commercially available flux core wire thus eliminating the need for additional fluxing of the aluminium product.